Hi, there! Thanks for reaching out.
To get your physical copy at cost, you don’t need to actually print a coupon. Together with your download files, there’s an external link that will take you to the page where you can buy it. The price you see there is already at 100% discount on revenue.
I hope this helps, but if you have any trouble finding it, please contact me at capacle@gmail.com and we work something out!